Intel® Optane™ Persistent Memory BIOS Optimization
Intel® Optane™ persistent memory 100 series (Intel® Optane™ PMem) coexists with traditional DDR4 DIMMs on the same bus. The memory controller in the 2nd Generation Intel® Xeon® Scalable processor arbitrates between the memory transactions coming from DRAM and Intel Optane PMem. Different arbitration profiles have been defined to determine the algorithm for when the memory controller switches between DRAM and Intel Optane PMem memory transactions. These profiles are configurable options through a persistent memory BIOS setting.
Previously, systems could choose profiles to either optimize DRAM bandwidth or latency. A new BIOS profile called Balanced Profile was developed to optimize Memory Mode performance. The three profiles now available include:
- Bandwidth Optimized Profile arbitrates between DRAM and Intel Optane PMem to maximize DRAM bandwidth on the memory bus.
- Latency Optimized Profile arbitrates between DRAM and Intel Optane PMem to minimize DRAM latency on the memory bus.
- Balanced Profile is optimized for Memory Mode by allowing the controller to switch more often between DRAM and Intel Optane PMem so that eviction transactions in DRAM can execute faster. In Memory Mode, DRAM is used as cache and Intel Optane PMem is used as volatile main memory to deliver DRAM-like performance, depending on the workload.
The CPU memory controller will first attempt to retrieve data from the DRAM cache. When the data is present, it will return the request from the DRAM cache, similar to the way DRAM access works today. When the data is not present, the request will be sent to Intel Optane PMem. The request is returned to the CPU and in parallel is sent to the DRAM cache. This extra request resulting from the cache miss in addition to the marginally higher latency of Intel Optane PMem when compared to DRAM can negatively impact performance. Balanced Profile optimizes Memory Mode performance by balancing the thresholds between DRAM and Intel Optane™ PMem to improve the bandwidth for all DRAM cache misses while maintaining the performance of DRAM cache hits.
Intel worked with server OEM partners to release this new persistent memory BIOS setting. These OEMs include Cisco, Dell, HPE, Inspur, Lenovo, and Supermicro (in addition to Intel® server boards). Contact your preferred OEM vendor for more information, as the setting may not be the default.